Page 1539 - Clinical Small Animal Internal Medicine

167 Otitis 1477

Table 167.5 Systemic glucocorticoid therapy for use in otitis
VetBooks.ir Glucocorticoid Dosage (mg/kg) Comments
externa and media

Prednisolone 1.0–2.0 PO q24h Should be
reduced to an
Methylprednisolone 0.8–1.8 PO q24h alternate‐day
Triamcinolone 0.1–1.8 PO q24h regime after two
acetonide weeks then
completely
tapered

Dexamethasone 0.1–0.2 IV Given as a single
treatment at the
time of ear flush;
may be repeated
at subsequent
rechecks after Figure 167.7 Nasopharyngeal polyp in a cat.
7–10 days if
other
glucocorticoids
are not being Signalment
used
When otitis media occurs as an extension from otitis
PO, by mouth (per os). externa, it most commonly affects middle‐aged or older
dogs. Occasionally, younger dogs may be affected. Breeds
that are predisposed to otitis externa will also be suscep-
tible to developing otitis media. Nasopharyngeal polyps
Otitis Media can be seen in any age of cat, including very young
kittens (Figure 167.7).
Primary secretory otitis media can be seen in young to
Etiology/Pathophysiology
middle‐aged Cavalier King Charles spaniels.
Otitis media is inflammation of the middle ear and
is often bacterial in origin. The organisms most com- History and Clinical Signs
monly isolated are Staphylococcus pseudintermedius,
Pseudomonas spp., Escherichia coli, Proteus spp., and Approximately 50–80% of all dogs with otitis externa of
Enterococcus faecalis. Occasionally, Malassezia pachy- more than six months duration will have otitis media.
dermatis may be involved. In most cases, infectious otitis Owners often report that dogs shake their heads and are
media is secondary, resulting from a descending infec- reluctant to open their mouths to, for example, carry a
tion as an extension of otitis externa, rather than an ball, yawn, bark or eat hard food. This is generally due to
ascending infection from the oropharynx or a result of pain in the region of the temporomandibular joint. Owners
hematogenous infection. Other causes of otitis media may complain that their dog’s hearing has deteriorated,
include primary secretory otitis media (PSOM) princi- which may be due to conductive changes in hearing as a
pally recognized in the Cavalier King Charles spaniel, result of fluid within the middle ear or cochlear damage if
foreign bodies, nasopharyngeal polyps seen most com- infection has spread to the inner ear. Neurologic signs in
monly in cats and neoplasms such as squamous cell car- the form of ataxia or nystagmus are more suggestive of oti-
cinomas and lymphoma. tis interna than otitis media. Cranial nerve dysfunction
Secondary otitis media is caused by the drainage of which can be seen with otitis media includes Horner syn-
exudate and infectious organisms into the tympanic drome, especially in cats, facial nerve paralysis and kerato-
bulla from the external ear canal. This causes inflamma- conjunctivitis sicca which can occur due to damage to the
tion to the lining epithelium, the mucoperiosteum, which parasympathetic innervation of the lacrimal gland.
forms a pseudostratified columnar epithelium contain-
ing increased numbers of secretory cells and glands. As a Diagnosis
result of ongoing inflammation, granulation tissue forms
within the bulla. With more chronic disease, this devel- The principal steps in diagnosis are otoscopy, myrin-
ops into dense connective tissue and, with time, bone gotomy, and diagnostic imaging. Otoscopy is an insen-
spicules may develop within this dense tissue. sitive modality for diagnosing otitis media. Where the